Blackout: How energy storage averted a UK-wide disaster

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On August 9, 2019, just five minutes before millions of commuters were set to head home for the weekend, disaster struck the UK’s power infrastructure. Jordan O’Brien, contributing editor, looks at the lessons we can learn from the recent UK-wide power outage and the role energy storage can play in keeping the grid online. 

Described as an incredibly unlikely event, two power stations simultaneously went offline; the first a small gas-fired plant in Cambridgeshire, while the second was one of the world’s largest offshore wind farms. The result? More than a million people were left without power. 

The UK is no stranger to power outages, having previously experienced widespread disruption in 2003 and 2008, but those instances were mostly localised. In 2019, however, the blackout affected nearly every region in England and Wales, leading to widespread disruption. 

So, what went wrong? Well, that’s a complicated question, because the network performed exactly as expected. In fact, had it not been for the contingencies put in place by the National Grid, the UK could have faced a much greater outage than it did. 

Quick response

During a sharp drop in frequency, the National Grid’s procedure is to shut down parts of the system to protect the network. Then, additional power generation is brought online in order to plug the gap. Traditionally, this additional generation could be as simple as bringing a coal-fired power station online, although that’s not a quick job, and is one of the reasons that the power outages of 2003 and 2008 lasted for hours. 

Thankfully, in 2019 we don’t have to wait for a power station to come online. That’s because batteries have the capability of kicking into action in a matter of seconds. Their job isn’t simply to maintain the frequency through providing back-up power, however, as they also have an advantage power stations don’t have – the ability to consume surplus energy. 

Electrical Review spoke to several leading companies in the energy storage market to get their take on the role played by energy storage in keeping the grid online. 

Nicola Watson, technical lead, Electrical Design Engineering at RedT Energy Storage: 

Energy storage is an important provider of ‘flexible’ capacity on the UK electricity system and is ideally suited to responding quickly to events like this. Unlike conventional generators such as gas and diesel turbines, they also have the advantage of being able to provide bi-directional flexibility.

More and more cheap renewable, non-synchronous generation (mainly solar and wind power) is coming online every day. It is replacing conventional, synchronous generation such as coal-fired power plants, and as a result, overall system inertia is reducing. This creates a strong case to invest in energy storage, which can deliver the synthetic inertia required to support our future energy system. 

In order to provide maximum benefit, energy storage needs to be adopted across the entire system, both on a distributed level (alongside behind-the-meter renewables at industrial sites for example) and increasingly, at transmission level too. The responsibility does not rest on just one organisation or customer group, but clearly National Grid have a leadership role to play in the design and operation of the market for flexibility.

Energy storage played an important part in stabilising the grid during the recent disruption, but there simply wasn’t enough installed capacity to overcome a nearly 2GW shortfall in generation. The solution is clear, more energy storage needs to be deployed across the UK, not only managing load for end-users, but also balancing supply and demand at transmission level on a more centralised basis.

Jeremy Harrison, principal analyst, Delta-EE:

This blackout was an exceptional event and extremely rare in the UK, and clearly illustrates the very high level of reliability we have become accustomed to – which is no doubt why it was headline news. 

Could energy storage have helped prevent the blackout? Technically the answer is clearly yes: batteries are well suited to providing millisecond response time for grid stability – when National Grid tendered for a new sub-second response frequency product in 2016, all of the contracts were won by batteries. However, the blackout raises more fundamental and interesting questions around the future of the grid through the energy transition.

A simple but costly approach would be to reduce the risk of such a blackout by having a higher level of reserve contingency. It could include a number of technologies, including batteries, but somebody would have to pay for it. 

A different approach – preferred by Delta-EE as it’s potentially lower cost and more sustainable in the long term – would be to embrace the growth in distributed energy resources: namely, to use embedded generation, DSR and interconnected local energy systems, also known as microgrids, to provide an increased level of resilience.  

Marek Kubik, market director UK and Ireland, Fluence Energy:

Battery-based energy storage is an extremely fast-responding technology, which makes it an important tool for maintaining grid reliability and resilience. Storage can charge or discharge power within milliseconds as opposed to the minutes it takes fossil-fuel plants to ramp up. In emergencies, providing this kind of instant power can reduce or avoid the need for secondary actions such as cutting off demand.

While it may not have prevented the recent blackout, energy storage already played a demonstrably important role in limiting its severity. The National Grid ESO interim report on the incident highlighted that nearly 500 MW of battery storage on its network responded quickly to provide power and help stabilise frequency. Without batteries, the extent of the power cuts would have been deeper, and their duration longer.

Having a large enough fleet of fast-acting batteries could have contained the rate of change of frequency and possibly prevented the power cut outright. The confluence of events that caused the blackout was rare, which has triggered a debate on what might be the appropriate level of such assets to have on call at any given time.

Aside from helping regulate frequency, storage can help to balance voltage, provide digital inertia, smooth the intermittency of renewable resources and, of course, store electricity to be used when it is most needed.

These services are relevant for every grid in the world regardless of energy mix, but doubly so as increasing levels of renewable energy are deployed. Wind and solar are becoming the cheapest forms of electricity generation in a growing number of markets, but energy storage is critical to their integration.

In Ireland – where, at times, over 65% of electricity comes from wind -- steps have been taken to reward battery response times all the way down to 150 milliseconds, compared to the 10 seconds – or 10,000 miliseconds -- typically required in the UK. Having this kind of market incentive makes a huge difference in the ability to manage sudden changes in the careful balance power of supply and demand.

Jonathan Dinkeldein, director EMEA marketing communications and public affairs, Eaton:

The core issue behind the recent UK power cut was that the system operators were unprepared to provide the amount of support required to help stabilise the grid. Part of the answer to improve resilience in the future could lie in easing the requirements for Firm Frequency Response (FFR) in order to open the market to participants with smaller more distributed assets, as is already the case in the Nordic markets and Ireland. 

The Nordic market has for some time benefited from a very stable and beneficial regulatory environment with a careful introduction of new rules. The Nordics also benefit from a lower threshold to participate in Frequency Regulation (FR) tenders to help with grid stability, with a different price point per kW for small and large installations. This is important as it creates more opportunities for storage capacity behind-the-meter, where it is most efficient for the economy as it is where the largest number of services can be ‘stacked’ to enhance the economic value of those assets.

By participating in the frequency containment reserve energy market, UPS systems can aid the stability of a more renewable-rich power grid to support the UK's future power needs.

Paul Troughton, senior director of regulatory affairs, Enel X:

National Grid procures enough frequency response services from generators, batteries, and end-users to cope with the loss of a certain amount of generation without it leading to an unplanned blackout. There’s a cost-benefit trade-off: they could procure more, and hence protect against more unlikely events, such as what occurred on 9 August, but this would cost more.

Our experience in other markets shows that demand-side response can provide large volumes of fast frequency response services much more cost-effectively than either generation or batteries, but only if care is taken in the design of the service and the procurement method to avoid erecting unnecessary barriers to end-user participation. If National Grid can get this right, they could unlock a greater level of demand-side provision of frequency response services, and so reduce costs. Their current hodge-podge of different products and manual procurement methodologies is far from optimal.

If the costs are reduced substantially, then the cost-benefit trade-off will change, and it might be judged worthwhile to procure greater volumes so as to protect against more unusual events. But this won’t necessarily be the case: systems where they take a very sophisticated approach to frequency management, such as New Zealand, typically aim for events like this to occur on average once a decade, and it’s 11 years since the last one here.